Physics at Brandeis

Ever wondered what do bacterial colonies, algae, the cytoskeleton of a cell and self-diffusive colloids have in common? They are all examples of active materials! What are active materials? What makes them special?

The Brandeis Materials Research Science and Engineering Center will host a hands-on workshop on Active Matter on Wednesday, Feb. 20, 2013. The workshop involves experiments, simulations and theory, together with an overview of active materials research at the Brandeis MRSEC. It will be held in Shapiro Science Center from 9:00 am – 7:30 pm. Prof. Azadeh Samadani is hosting the workshop. The application deadline is Jan. 10, 2013 – apply here.

Ye Zhang, a Postdoctoral Fellow from Prof. Bing Xu’s research group at Brandeis, won the 2012 MRS Fall Meeting Poster Awards for her poster titled Self-oscillatory Hydrogels Driven by Belousov-Zhabotinsky Reaction within the symposium on Bioinspired Directional Surfaces-From Nature to Engineered Textured Surfaces & Precision Polymer Materials-Fabricating Functional Assemblies, Surfaces, Interfaces, and Devices. The goal of the project is to make materials that operate like synthetic cardiac or intestinal muscles; feed them and they will pump forever, or as long as the arteries remain open. Ye, the poster’s lead author, is a member of the Brandeis Materials Research Science and Engineering Center (MRSEC) working on project involving the groups of Profs. Bing Xu, Irving Epstein and Seth Fraden of the Chemistry and Physics Departments.

Ye’s work focuses on the development and study of active matter based on non-linear chemical dynamics, specifically the Belousov-Zhabotinsky reaction. Beginning two years ago she systematically modified a class of gels that exhibit periodic volume oscillations which were produced by other groups. First, Ye succeeded in significantly improving the amplitude of volume oscillations. Next, she developed several novel self-oscillatory systems and established a systematic way to improve the bulk material properties of the synthetic heart.  To build a reliable beating heart, Ye optimized the molecules building the material at the molecular level of tens to hundreds of atoms, or scales of 1 nm and then figured out how to assemble them into networks of polymers on the scales of 10 – 100 nm, and then further assembled them on a longer length scale, into elastic networks on the scales of microns, and finally sculpted the resulting rubbery materials using photolithographic and microfluidic methods into useful shapes for study and application. Ye’s award is a recognition of her contribution to molecular engineering and serves as a quintessential example of the  “bottom-up” construction methods exemplified by the interdisciplinary teams of the Brandeis MRSEC.

 
On November 28, NASA posted a press release announcing the record breaking discovery of an x-ray emitting jet in a quasar at a distance of 12.4 billion light years from Earth. The discovery is published in the Astrophysical Journal Letters, and the lead author is C. (Teddy) Cheung (Brandeis PhD 2004). Co-authors include Doug Gobeille (Brandeis PhD 2011), Brandeis professor of astrophysics John Wardle, and colleagues from the Harvard-Smithsonian Center for Astrophysics. Teddy Cheung made the x-ray image, using the orbiting Chandra X-ray observatory, and Doug Gobeille made the radio image as part of his PhD research at Brandeis using the 27 antennas of the Very Large Array in New Mexico.

A jet of X-ray emitting plasma from a supermassive black hole 12.4 billion light years from Earth has been detected by NASA’s Chandra X-ray Observatory. This is the most distant X-ray jet ever observed and gives astronomers a glimpse into the explosive activity associated with the growth of supermassive black holes in the early universe. The jet was produced by a quasar named GB 1428+4217, or GB 1428 for short. Giant black holes at the centers of galaxies can pull in matter at a rapid rate producing the quasar phenomenon. The energy released as particles fall toward the black hole generates intense radiation and powerful beams of high-energy particles that blast away from the black hole at nearly the speed of light. These particle beams can interact with magnetic fields or ambient photons to produce jets of radiation.

“We’re excited about this result not just because it’s a record holder, but because very few X-ray jets are known in the early universe,” said Teddy Cheung of the National Academy of Sciences, resident at the Naval Research Laboratory in Washington DC, and lead author of the paper describing these results.

As the electrons in the jet fly away from the quasar, they move through a sea of background photons left behind after the Big Bang. When a fast-moving electron collides with one of these so-called cosmic microwave background photons, it can boost the photon’s energy into the X-ray band.

“Since the brightness of the jet in X-rays depends, among other things, on how fast the electrons are moving away from the black hole, discoveries like the jet in GB 1428 tell us something about the environment around supermassive black holes and their host galaxies not that long after the Big Bang,” said co-author Lukasz Stawarz from the Japan Aerospace Exploration Agency, in Kanagawa, Japan.

Because the quasar is seen when the universe is at an age of about 1.3 billion years, less than 10% of its current value, the cosmic background radiation is a thousand times more intense than it is now. This makes the jet much brighter, and compensates in part for the dimming due to distance.

“We’re lucky that the universe gives us this natural amplifier and lets us detect this object with relatively short exposures,” said co-author Aneta Siemiginowska, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, “Otherwise we might miss important physical processes happening at very large distances from Earth and as far away as GB 1428.”

While there is another possible source of X-rays for the jet — radiation from electrons spiraling around magnetic field lines in the jet — the authors favor the idea that the cosmic background radiation is being boosted because the jet is so bright.

Prior to the discovery of the jet in GB 1428, the most distant X-ray jet known was 12.2 billion light years away, and another is located at about 12 billion light years, both discovered by authors of the GB 1428 paper. A very similar shaped jet in GB 1428 was also detected in radio waves with the NSF’s Very Large Array (VLA).

The particle beams that produce these three extremely distant X-ray jets appear to be moving slightly more slowly than jets from galaxies that are not as far away. This may be because the jets were less energetic when launched from the black hole or because they are slowed down more by their environment.

The researchers think the length of the jet in GB 1428 is at least 230,000 light years, or about twice the diameter of the entire Milky Way galaxy. This jet is only seen on one side of the quasar in the Chandra and VLA data. When combined with previously obtained evidence, this suggests the jet is pointed almost directly toward us. This configuration would boost the X-ray and radio signals for the observed jet and diminish those for a jet presumably pointed in the opposite direction.

Observations were also taken of GB 1428 with a set of radio telescopes at different locations around the Earth that allows details to be resolved on exceptionally small scales. They revealed the presence of a much smaller jet, about 1,900 light years long, which points in a similar direction to the X-ray jet.

This result appeared in the September 1st, 2012 issue of The Astrophysical Journal Letters. Other co-authors of the paper are Doug Gobeille from University of South Florida in Tampa, FL; John Wardle from Brandeis University in Waltham, MA; and Dan Harris and Dan Schwartz from the Harvard-Smithsonian Center for Astrophysics.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
More information, including images and other multimedia, can be found at: http://www.nasa.gov/chandra and http://chandra.si.edu

Three hundred feet beneath Geneva, Switzerland, lies the world’s biggest machine, so vast it spills over the neighboring French border — not just in one place, but in four separate locations.

The Large Hadron Collider (LHC) is the biggest and baddest physics experiment ever created. Inside a subterranean tunnel, a 17-mile ring of high-powered magnets flings subatomic particles along at nearly the speed of light, slamming them together in spectacular collisions that can reveal their basic building blocks.

To the untrained eye, it looks like the Death Star crammed into a mine shaft.

To experimental physicists like Brandeis’ Jim Bensinger, Craig Blocker and Gabriella Sciolla, though, the collider embodies the greatest aspirations of particle physics: the quest to understand, as closely as possible, the forces that are locked inside the most infinitesimal specks of matter, and the laws that govern that matter.

Read the entire  Brandeis Magazine article.

Life is on the move! Motion is ubiquitous in biology. From the gargantuan steps of an elephant to the tiniest single celled amoeba, movement in biology is a complex phenomenon that originates at the cellular level and involves the organization and regulation of thousands of proteins. These proteins do everything from mixing the cytoplasm to driving cell motility and cell division. Deciphering the origins of motion is no easy feat and scientists have been studying such complex behavior for quite some time. With biology as an inspiration, studying these complex behaviors provides insight into engineering principals which will allow researchers to develop an entirely new category of far-from-equilibrium materials that spontaneously move, flow or swim.

In a recent report in the journal Nature, a team of researchers from Brandeis University consisting of Tim Sanchez, Daniel T. N. Chen, Stephen J. DeCamp, Michael Heymann, and Zvonimir Dogic have constructed a minimal experimental system for studying far-from-equilibrium materials. This system demonstrates the assembly of a simple mixture of proteins that results in a hierarchy of phenomena. This hierarchy begins with extending bundles of bio-filaments, produces networks that mix themselves, and finally culminates in active liquid crystals that impart self-motility to large emulsion droplets.

Their system consists of three basic components: 1) microtubule filaments, 2) kinesin motor proteins which exert forces between microtubule filaments, and 3) a depletion agent which bundles microtubule filaments together. When put together under well-defined conditions, these components form bundled active networks (BANs) that exhibit large-scale spontaneous motion driven by internally generated active stresses. These motions, in turn, drive coherent fluid flows. These features bear a striking resemblance to a biological process called cytoplasmic streaming, in which the cellular cytoskeleton spontaneously mixes its content. Additionally, the system has great potential for testing active matter theories because the researchers can precisely tune the relevant system parameters, such as ATP and protein concentration.

 

The researchers also demonstrate the utility of this biologically-inspired synthetic system by studying materials science topics that have no direct biological analog. Under dense confinement to an oil-water interface, microtubule bundles undergo a spontaneous transition to an aligned state. Soft matter physics describes such materials as liquid crystals, which are the materials used to make liquid crystal displays (LCDs). These active liquid crystals show a rich variety of dynamical behavior that is totally inaccessible to their equilibrium analogs and opens an avenue for studying an entirely new class of materials with highly desirable properties.

Lastly, inspired by streaming flows that occur in cells, the researchers encapsulate the bundled active networks into spherical emulsion droplets. Within the droplet, microtubules again formed a self-organized nematic liquid crystal at the oil-water interface. When the droplets were partially squished between glass plates, the streaming flows generated by the dynamic liquid crystals lead to the emergence of spontaneous self-motility.

This research constitutes several important advances in the studies of the cytoskeleton, non-equilibrium statistical mechanics, soft-condensed matter, active matter, and the hydrodynamics of fluid mixing. The researchers have demonstrated the use of biological materials to produce biomimetic functions ranging from self-motility to spontaneous fluid flows using fundamentally new mechanisms. Additionally, the experimental system of bundled active microtubules is poised to be a model for exploring the physics of gels, liquid crystals, and emulsions under far-from-equilibrium conditions.

To see more videos from the Dogic lab at Brandeis University, check out their YouTube page.

Gregory Widberg is the Sr. Mechanical Engineer in the Physics department who also works with other departments in the Division of Science repairing scientific equipment.  Greg was called to active duty and served in Afghanistan from 2011 to 2012 as the Command Sgt. Major for the 1st Battalion, 182nd Infantry Regiment.  Greg is shown accepting the Walter T. Kerwin Jr. Readiness Award in a ceremony in Washington, DC on October 23, 2012.  The award is presented to the battalion with the highest level of readiness in its respective component.

The 52nd New England Complex Fluids Workshop will be held on September 21, 2012. hosted by the Brandeis MRSEC. The workshop will feature a panel of researchers from industry exploring the academic / industrial relationship. Additionally, we will have one session of invited academic speakers, plus  two contributed “sound bite” sessions. Please consider submitting your work for an oral presentation.

In addition to taking questions from the floor, the panel will address questions such as  what kind of training and education do industrial labs seek in job applicants? What (scientific) knowledge should applicants possess? experience? skills? creativity? business knowledge? What should the universities do to better prepare students for a career in industry? What opinion do the industrial scientists and managers have on the research being done at universities? And how does research done in industry compare to that done in universities?  How common are collaborations between industry and academic researchers? What makes a successful collaboration? When does industry use academic consultants?

Registration (free) required: http://complexfluids.org/ (deadline: 8am, September 19, 2012)

SCHEDULE