Barry and Dogic receive 2010 Cozzarelli Prize

Physics graduate student Edward Barry and Professor Zvonimir Dogic have been selected to receive the 2010 Cozzarelli Prize in Engineering and Applied Sciences from the Proceedings of the National Academy of Sciences (PNAS) for their work entitled “Entropy driven self-assembly of non-amphiphilic colloidal membranes.”

The work of Barry and Dogic was selected for exploring a novel pathway for the self-assembly of 2D fluid-like surfaces or monolayer membranes from non-amphiphilic molecules. Amphiphilic molecules consist of immiscible components, such as a hydrophobic tail and a hydrophilic head, which are irreversibly linked to each other, thus frustrating their bulk separation. When added to water, these molecules self-assemble into a variety of structures in order to satisfy competing affinities for the solvent. One particular structure, a bilayer membrane, which is a thin flexible sheet with remarkable mechanical and chemical properties, plays an essential role in biology, physics, and material science. Over the past decade the paramount example of conventional amphiphilic self-assembly has inspired the synthesis of numerous amphiphilic-type building blocks for studies of membrane self-assembly including various block-copolymers, heterogeneous nanorods, and hybrid protein-polymer complexes. Underlying all of these studies is the belief that amphiphilic molecules are an essential requirement for membrane assembly.

Barry and Dogic, using a combination of theory and experiments, describe for the first time a set of design principles required for the assembly of non-amphiphilic membranes in which the constituent rod-like molecules are chemically homogeneous.  Using a simple mixture of filamentous bacteriophages and non-adsorbing polymer, they were able to assemble macroscopic membranes roughly 4-5 orders of magnitude larger than the constituent molecules themselves. Due to unique properties of their system, Barry and Dogic were able to characterize the physical behavior of the resulting non-amphiphilic membranes at all relevant length scales and provide an entropic mechanism that explains their stability. The importance of these results lies in their potential to establish a fundamentally different route toward solution based self-assembly of 2D materials.

Papers selected for the Cozzarelli Prize were chosen from more than 3,700 research articles published by PNAS in 2010 and represent the six broadly defined classes under which the National Academy of Sciences is organized. The award was established in 2005 and named the Cozzarelli Prize in 2007 to honor late PNAS Editor-in-Chief Nicholas R. Cozzarelli. The annual award acknowledges recently published papers that reflect scientific excellence and originality. The 2010 awards will be presented at the PNAS Editorial Board Meeting, and awardees are recognized at the awards ceremony, during the National Academy of Sciences Annual Meeting on May 1, 2011, in National Harbor, Maryland.

An outstanding referee

Refereeing papers, like refereeing sports, can be a thankless task. Reading and reviewing papers on short deadlines for pushy editors for no financial gain and little recognition is a duty taken on by academics, who often seem to like nothing better than to complain about it.  Perhaps in recognition of this, the American Physical Society has initiated a selective award program to recognize scientists who have been exceptionally helpful in assessing manuscripts for publication in the APS journals. The program annually recognizes approximately 150 of the 45,000 currently active referees.  Among the 144 Outstanding Referees of the Physical Review and Physical Review Letters journals, as chosen by the journal editors for 2011, is Professor Robert Meyer of the Brandeis Physics department.

Schweber receives 2011 Abraham Pais Prize for History of Physics

Silvan “Sam” Schweber, Professor of Physics, emeritus and Richard Koret Professor in the History of Ideas, is the recipient of the 2011 Abraham Pais Prize for History of Physics “for his sophisticated, technically masterful historical studies of the emergence of quantum field theory and quantum electrodynamics, and broadly insightful biographical writing on several of the most influential physicists of the 20th century: Einstein, Oppenheimer, and Bethe”.  Prof. Schweber has been a member of the Brandeis Physics Department since 1955.

ATLAS finds evidence for a quark-gluon plasma

The ATLAS Experiment, in which the Brandeis High Energy Physics Group participates, has announced evidence for a quark-gluon plasma. This is a state of matter that existed for the first few microseconds after the birth of the Universe when quarks and gluons roamed freely before the Universe cooled enough for them to combine into the protons and neutrons that make up the matter we know today. A phenomenon known as jet quenching, which is considered evidence for the production of a quark-gluon plasma, has been observed and accepted for publication in Physical Review Letters.

ATLAS is one of the experiments at the Large Hadron Collider (LHC). We have just completed a successful first year of running. At the end of the run we studied Heavy Ion collisions (lead on lead). Head-on collisions by two lead nuclei are expected to produce a quark-gluon plasma. In this process, the products of hard collision (jets) are reabsorbed by the plasma. Observation of this process by ATLAS is considered evidence for the production of a quark-gluon plasma. Being able to produce and study this phenomenon will help us understand behavior of matter at the very beginning of the Universe.

More information about this phenomenon and details about the ATLAS experiment can be found at the http://atlas.ch/ web site. The Brandeis High Energy Physics Group includes professors Jim Bensinger, Craig Blocker, Larry Kirsch, Gabriella Sciolla, Hermann Wellenstein and research scientist Christoph Amelung.

Chirality leads to self-limited self-assembly

Simple building blocks that self-assemble into ordered structures with controlled sizes are essential for nanomaterials applications, but what are the general design principles for molecules that undergo self-terminating self-assembly? The question is addressed in a recent paper in Physical Review Letters by Yasheng Yang, graduate student in Physics, working together with Profs. Meyer and Hagan,  The paper considers molecules that self assemble to form filamentous bundles, and shows that chirality, or asymmetry with respect to a molecule’s mirror image, can result in stable self-limited structures. Using modern computational techniques, the authors demonstrate that chirality frustrates long range order and thereby terminates assembly upon formation of regular self-limited bundles.  With strong interactions, however, the frustration is relieved by defects, which give rise to branched networks or irregular bundles.

Figure: (a) Snapshots of regular chiral bundles. Free energy calculations and dynamics demonstrate that the optimal diameter decreases with increasing chirality. (b) Branched bundles form with strong interactions

NSF gives Zvonimir Dogic Teacher-Scholar award

Asst. Professor of Physics Zvonimir Dogic has won a $500,000 award from the National Science Foundation (NSF) Early Career Development Program. The five-year award supports junior faculty who “exemplify the role of teacher-scholars through oustanding research, excellent education, and the integration of education and research within the context of the mission of their organizations,” according to the NSF. Dogic’s research seeks to explain how biopolymers organize themselves into macroscopic materials.

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