Eric Sembrat's Test Bonanza

The ATLAS Experiment at the Large Hadron Collider with its sister experiment CMS reported a discovery last summer of a new boson which is consistent with the Standard Model Higgs boson.  The Higgs particle has been searched for decades. It is the final jewel in the Standard Model of particle physics, a crowning achievement of 20th century science that gives a powerful understanding of fundamental particles and their interactions. In the Standard Model, the Higgs is the quantum of a field that accounts for the masses of those particles.  We will describe the apparatus, the data and other searches. 

Relics of early life, preceding even the last universal common ancestor of all life on Earth, are present in the structure of the modern day canonical genetic code --- the map between DNA sequence and amino acids that form proteins.  The code is not random, as often assumed, but instead is now known to have certain error minimization properties.  How could such a code evolve, when it would seem that mutations to the code itself would cause the wrong proteins to be translated, thus killing the organism?  Using digital life simulations, I show how a unique and optimal genetic code can emerge over evolutionary time, but only if horizontal gene transfer --- a network effect --- was a much stronger characteristic of early life than it is now.  These results suggest a natural scenario in which evolution exhibits three distinct dynamical regimes, differentiated respectively by the way in which information flow, genetic novelty and complexity emerge. Possible observational signatures of these predictions are discussed.

Icicles are harmless and picturesque winter phenomena, at least in cold climates.  The shape of an icicle emerges from a subtle feedback between ice formation, which is controlled by the release of latent heat, and the flow of water over the evolving shape.  The water flow, in turn, determines how the heat flows.  The air around the icicle is also flowing, and all forms of heat transfer are active in the air.  Ideal icicles are predicted to have a universal "platonic" shape, independent of growing conditions.  In addition, many natural icicles exhibit a ripply shape, which is the result of a morphological instability.  The wavelength of the ripples is also remarkably independent of the growing conditions.  Similar shape and ripple phenomena are also observed on stalactites, although certain details of their formation differ.  We built a laboratory icicle growing machine to explore icicle physics. We learned what it takes to make a platonic icicle and the surprising origin of the ripples.

FREE TICKETS AVAILABLE FOR A LIMITED TIME AT www.squishyphysics.eventbrite.com

I present inelastic neutron scattering data from one- two- and three-dimensional insulating magnetic materials at low temperatures that do not display a coherent resonant mode of excitation. Instead, momentum resolved spectra take the form of bounded continua. I interpret the spectra as evidence for fractionalization of a spin flip into distinct quasi-particles.

The unifying feature of the quantum magnets examined is a ground state that does not break rotational or translational symmetries – conventional Neel order having been disfavored by competing interactions and/or low dimensionality. I discuss the nature of the quasi-particles based on the neutron scattering data, the underlying lattice structure, and the spin Hamiltonian. 

The talk features inelastic neutron scattering data from novel instrumentation at the NIST Center for Neutron Research and the ORNL Spallation Neutron Source, which is dramatically improving our ability to probe atomic scale dynamics in condensed matter.

 * Also at NIST and ORNL. Work at IQM is supported by DoE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-08ER46544

A quantum processor,  using quantum states of light and matter, holds the promise of performing calculations and simulations that are not practical by a classical processor. Many of the key components for a quantum processor have been demonstrated by various research groups and we can expect these components to be integrated into basic quantum processors in the near future. However, there remain significant technical challenges in scaling the system size and making the system robust and flexible. In GTRI ‘s Quantum Information Systems (QIS)  Group, we use atomic ions as our quantum system and are developing scalable technologies for trapping ions and manipulating the quantum information the ions hold as well as tools to run an eventual processor. I will give an overview of the technologies being developed at GTRI and the efforts to make a quantum processor user friendly.

One of the long term challenges in human health and disease is the control of pathogens, such as antibiotic-resistant forms of bacteria. In this talk, we will briefly describe two directions where soft condensed matter physics based approaches have been useful.

1)     Bacterial biofilms are structured multi-cellular communities that are notoriously resistant to antibiotics. We translate bacteria movies into searchable databases of bacterial behavior via methods adapted from colloid physics, and find an unexpected diversity in motility driven by Type IV pili across different bacterial species.  The associated phenomena include ‘stick-slip’ motion analogous to earthquake dynamics, and self-organization in early biofilm development reminiscent of capitalist economies.

2)     We examine the mechanism of a range of pore-forming polypeptides, including antimicrobial peptides, cell penetrating peptides, viral fusion peptides, and apoptosis proteins, and show how a combination of geometry, coordination chemistry, and soft matter physics can be used to approach a unified understanding.  

Despite their natural abundance and wide industrial applications, such as red blood cells and clay, disks are the least studied colloidal systems compared to geometries like spheres and rods. We have established methods to fabricate and control the size, aspect ratio, and polydispersity of disks and systematically investigate their effects on discotic liquid crystal phase transitions. This talk will focus on surface controlled shape design of discotic microparticles using phase changing emulsions and the observation of the discotic smectic phase using nanoplates with identical thickness. Recent results such as discotic liquid crystals emulsions, gelation via ionic exchange, depletion attraction induced liquid crystal phase transition, iridescence from layered structure, and nematic hydrogels will briefly presented. Comprehensive understanding of the colloidal discotics in terms of complex fluids behaviors and liquid crystal transitions will help establish theory for model atomic liquid crystals and develop industrial applications.

Biography

Professor Cheng obtained his PhD degree from the Physics Department of Princeton University in 1999. He has his MS degree from the Institute of High Energy Physics (Beijing) in 1993 and BS degree from the Modern Physics Department of University of Science and Technology of China in 1990. He was a postdoctoral fellow of ExxonMobil Research and Engineering Company (Annandale, New Jersey, USA), and Harvard University (with Prof. Dave Weitz). He joined Texas A&M University as an Assistant professor in the Artie McFerrin Department of Chemical Engineering in August 2004 and was promoted to Associate professor in 2010.  He is also a faculty member of the Materials Science and Engineering Program and the Professional Program in Biotechnology of TAMU. Professor Cheng’s expertise is in the area of complex fluids and soft condensed matter physics. He has published over 60 papers in journals including Nature, Science, and Physical Review Letters.

PLEASE NOTE: This is a WEBINAR

Accurate modeling of blood flow provides insights into arterial stent design, surgical planning, and analysis of stroke risk. Unfortunately, fully detailed modeling of the cardiovascular system is computationally impossible due to the enormous number of blood vessels in the body.  Instead, a common technique is to choose a small subset of arteries to model in detail while accounting for the "un-modeled" parts of the cardiovascular system through boundary conditions.  A popular tactic for deriving such a boundary condition is to analytically solve a simple blood flow model in an idealized self-similar tree of arteries.  This technique, termed the "structured tree" boundary condition, is computationally cheap but is not broadly applicable since it assumes temporal periodicity.  We have developed a generalized version of the structured tree condition that lacks this restriction and is applicable to general transient flow regimes.  We will discuss the derivation of this condition and its nontrivial numerical implementation.  Additionally, computational results and a comparison to the original structured tree condition for periodic problems will be provided.

PLEASE NOTE: This is a WEBINAR

A problem of practical interest in control theory is to stabilize a nonlinear dynamical system through the action of a feedback control.  The stabilization problem can be embedded as an optimal control problem leading one to solve a Hamilton-Jacobi (HJ) PDE.  The associated HJ equation is a first order nonlinear singular PDE and, under suitable conditions, can be solved locally using power series methods.  In this talk, I will present a numerical method that extends the domain of validity of the power series approach.  The method relies on patchy vector field techniques, level set methods, and a Cauchy-Kowalevski continuation algorithm.  The method will be illustrated on 2D-3D control systems.