Nimrod Segall

PhD Student 
Computational Soft and Active matter
Tel Aviv University
nimrods6@mail.tau.ac.il
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Contact Me


If you have any questions, any ideas regarding my work, or if you just want to chat or say hi, send me an e-mail on  nimrods6@mail.tau.ac.il .

If you're ever in Tel Aviv and wish to give a talk on subjects relating to soft matter physics or biophysics at the Biosoft Center Seminar , send me an email to  biosoftc@tauex.tau.ac.il .


My Office is located in Tel Aviv University in Wolfson Mechanical Engineering 224, phone +972-3-640-5299.

Jamming vs. Caging in 3D

In 2D Jamming = Caging. In 3D that does not have to be the case!




Glassy behavior is observed not only in 'chemical' glasses, but also in granular materials and colloidal suspensions. These systems are characterized by having a glass transition temperature. That is, a temperature in which a mixed order out of equilibrium phase transition occurs and the relaxation times of the system diverge.


This critical slowing down in dynamics is one among many reasons as to why studying glassy behavior is challenging both experimentally and theoretically. Kinetically constrained models have been successful in this as they are simple enough to easily simulate large systems and are sometimes analytically solvable.

Formation of cages in the 3D extension of the Spiral Model

We have studied a three dimensional  [1] extension of the 2D Spiral Model   [2]. The 2D model undergoes jamming at a critical density in which a fraction of the particles in the system cannot move anymore and form 1D clusters of frozen sites.  The particles that can still move become rattlers - they are confined to some local area of the system and cannot diffuse far away.

In 3D however, that is not the case; a fraction of the particles in the system become frozen and creates a 1D frozen cluster, however mobile particles can diffuse over long distances. The reason is geometric - in 2D one-dimensional frozen clusters of particles act as effective walls, and particles are unable to cross these walls and travel to the other side. In 3D particles use the third dimension to travel around these clusters. We investigated the existence of a second critical density, one in which frozen clusters become 2D and particles become confined in local cages in the system.

The probability an infinite cage exist as a function of density of free volume sites. Two phase transitions appear, one for jamming and the other for caging. The jamming transition relates to directed percolation while the caging transition is a random percolation transition.

Using a fast and efficient culling algorithm, we bypass running the dynamics of the system and find the underlying structural property of the system determining the diffusivity of particles.


We indeed find a second critical density. Its critical exponents value agree with those of random percolation.

My Research Interests

My research focus is on glassy dynamics, jamming, active frustrated materials and active living matter.

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Jamming vs. Caging in 3D


In 2D a system undergoing jamming will cause particles to be confined in local cages. In 3D however that does not have to be the case - frozen clusters of particles appear at a density in which particles may still diffuse across the system. Only at a higher density particles become caged. The reason is geometrical. We use a fast algorithm bypassing the need to run the dynamics of the system to uncover the underlying structure of the system ...




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Formation of cages in the 3D extension of the Spiral Model
My MSc Thesis
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CV
Work Experience
  • Tel Aviv University, Teaching Assistant; General Chemistry 1 (Chemistry Department), Kinetics (Chemistry Department). Homework grading.
  • Private Tutor; Physics, Mathematics, Chemistry.

Academic Record

  • BSc. - Tel Aviv University, Raymond and Beverly Sackler faculty of exact sciences, school of chemistry.
  • MSc. - Tel Aviv University, Raymond and Beverly Sackler faculty of exact sciences, school of chemistry.

List of Publication

  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three-Dimensional Jamming Percolation. Journal of S tatistical Mechanics - Theory and Experiment, 054051 (2016). 
  • N. Segall, E. Teomy, and Y. Shokef, The critical density in 3D jamming percolation, In preparation...

Work Presented In

Talks:

  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three Dimensional Jamming Percolation, Israel Physical Society, Bar-Ilan University 2015.
  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three Dimensional JammingPercolation, The Raymond and Beverly Sackler Center for Molecular and Materials Science Retreat, Neve-Ilan 2015.
Posters:
  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three Dimensional Jamming Percolation, Mechanical Instabilities in Solids, The Hebrew University 2017. Poster.
  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three Dimensional Jamming Percolation, Stochasticity of Cells and Genes, Tel-Aviv University 2016. Poster.
  • N. Segall, E. Teomy, and Y. Shokef, Jamming vs. Caging in Three Dimensional Jamming Percolation, Viscous Liquids IV, University of Montpellier, France 2015. Poster.

Other

  • I attended the 2015 Boulder School: Soft Matter In and Out of equilibrium.
  • I am currently the Biosoft Seminar coordinator in Tel Aviv University:  Biosoft Center
Nimrod Segall, MSc

I am an engineering grad student in Tel Aviv University, currently working on my PhD under the supervision of Yair Shokef.

My research focus is on glassy dynamics, jamming, active frustrated materials and active living matter, mostly using computational tools to tackle these subjects.

I have a  multidisciplinary background; undergrad in Chemistry, Master thesis on jamming and caging in glassy systems, and my current work is on the subject of active frustrated materials.

News

Formation of cages in the Spiral Model's Jammed State [1]
Nimrod Segall, Computational Soft and Active Matter
 Tel Aviv University, Wolfson Engineering 224
nimrods6@mail.tau.ac.il +972-3-640-5299