Gelation without Attraction

By Bulbul Chakraborty

Gels are one of the most puzzling of all solids. Originally coined as a short form of gelatin, gels can be jelly-like as in Jello, or quite hard as in silica gels. They appear in suspensions of particles at extremely low volume fractions, and yet they are rigid. The conventional wisdom is that gels are a consequence of arrested phase separation of the suspended particles from the fluid. A natural mechanism for the arrest is attraction between the particles, which leads to the formation of filamentous networks of particles weaving through the suspending fluid.

Attraction has been viewed as being essential to the formation of gels. However, a new study published in Physical Review Research led by Carl Merrigan from the Chakraborty group, shows that “active particles” can gel even in the absence of physical attraction. Active matter, composed of particles that convert ambient energy to directed motion, has emerged as an important model for the collective behavior of biological matter such as bacterial suspensions. Using a combination of theoretical analysis and numerical simulations, the collaboration between the groups of Chakraborty and Shokef (Tel Aviv University) showed that the directed motion acts like an effective attraction, leading to gelation of the active particles.

The figure below shows the structure of these gels. As the particles become more active, they jam into clusters of immobile particles (red) surrounded by fluid regions (blue), and often opening up voids. Intriguingly, these active particles, which repel each other also show a transition from a dense glassy solid to a gel as the speed of directed motion is increased. The remarkable similarity between the behavior of passive particles with attraction and active particles suggests that biological entities could form solid-like aggregates without any physical or chemical attraction, purely as a consequence of their dynamics.

Reasearch image from Gelation without Attraction post

SPROUT and I-Corps Applications are Open

Sprout logoThe Brandeis Innovation SPROUT and I-Corps programs offer support for bench and non-bench research. Both programs offer funding in different amounts, mentorship, training and help in further exploring the commercial potential of inventions. SPROUT supports bench research, while I-Corps emphasizes training for both bench and non-bench researchers in developing the commercial potential of discoveries, with small grants and extensive training programs. You can apply to one or both programs.

  • If you have a technology / solution that you have started developing and you would like to get funding for it via SPROUT and/or I-Corps, then please complete this form
  • If you do not already have a technology, then you can complete this form to qualify for the I-Corps training program and be matched with a team

Icorps logo

SPROUT teams will get the chance to qualify for up to $30,000 in funding. The I-Corps program provides entrepreneurial training and covers the core of commercializing a technology or building a startup. It comes with an NSF $750 travel and training stipend and an NSF I-Corps certificate/digital badge.

Apply by February 25, 2020 at 11:59PM

John Wardle part of team that produces first-ever black hole image

Credit: Event Horizon Telescope Collaboration

John Wardle, Professor of Astrophysics and the Head of the Division of Science, has been playing an integral role in bringing the first-ever image of a black hole to realization. Announced today, the image of the M87 black hole is being hailed as a major scientific breakthrough. Wardle serves on four of the Event Horizon Telescope’s 23 working groups, helps analyze the polarization of the M87 black hole’s radio emissions, and serves on the publication working group. This announcement was made in a series of six papers published in a special issue of The Astrophysical Journal Letters.

Read more: BrandeisNow, Event Horizon Telescope, NSF News Release

2019 SACNAS Regional Meeting to be held at Brandeis

Brandeis University will be hosting the 2019 New England SACNAS Regional Meeting on Saturday, March 23, 2019 from 9am-5pm.

SACNAS is an inclusive organization dedicated to fostering the success of Chicanos/Hispanics and Native Americans, from college students to professionals, in attaining advanced degrees, careers, and positions of leadership in STEM. More information about this event is available at the Brandeis SACNAS site.

Dr. Tepring Piquado, a Policy Researcher at RAND Corporation and Brandeis alum and Dr. Marcelle Soares-Santos, the Landsman Assistant Professor at Brandeis, will be keynote speakers. More information about the speakers and the Career and Professional development workshops and panel discussions are available as well.

This meeting is FREE, but all attendees must register by February 22, 2019.


Spencer Bloch to speak at 2018 Eisenbud Lectures

Eisenbud 2018 Poster

The 2018 Eisenbud Lectures in Mathematics and Physics will be held from November 13-15 at Brandeis University. This years speaker is Spencer Bloch, Professor of Mathematics at the Yau Mathematical Sciences Center at Tsinghua University, and Emeritus Professor of Mathematics at the University of Chicago.

Professor Bloch is a mathematician whose work has influenced many subjects including number theory, algebraic geometry and mathematical physics. The following lectures will be informative and entertaining:

  • Tuesday, November 13 at 4pm: “Multiple Zeta Values and Mixed Tate Motives over ℤ”  (intended for a general audience) Location: Abelson 131.
  • Wednesday, November 14 at 4pm: “Motivic Γ-functions” (colloquium style lecture). Location: Brown 316.
  • Thursday, November 15 at 4pm, “Relative Completions,” Location: Goldsmith 317.

Refreshments will be served 15 minutes before each talk. There will be a reception in Abelson 333 following Tuesday’s talk.

The Eisenbud Lectures are the result of a generous donation by Leonard and Ruth-Jean Eisenbud intended for a yearly set of lectures by an eminent physicist or mathematician working close to the interface of the two subjects.

Brandeis IGERT Summer Institute Scheduled for June 25-28

The Brandeis IGERT program in “Geometry and Dynamics” is holding its Summer Institute from June 25-28. This is a series of lectures aimed at graduate students on the mathematical & theoretical side of the sciences, on a broad spectrum of topics — of course, postdocs, faculty, and sufficiently advanced undergraduates should enjoy these as well.

Once again we have an excellent list of speakers from inside and outside of Brandeis, on subjects including quantum computing, blockchain technology, origami, and the carbon cycle and mass extinction.  A full schedule is available. All are welcome and coffee and lunch will be provided: please RSVP here or by selecting the button at the bottom of the schedule page, so that we have an accurate headcount.

We hope to see you there!

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